Indirect ELISA for the detection of a specific antibody response againstMycoplasma gallisepticum

Establishment of a Mycoplasma hyorhinis challenge model in 5-week-old piglets

Introduction

Mycoplasma hyorhinis is an emerging swine pathogen with high prevalence worldwide. The main lesions caused are arthritis and polyserositis, and the clinical manifestation of the disease may result in significant economic losses due to decreased weight gain and enhanced medical costs. We aimed to compare two challenge routes to induce M. hyorhinis infection using the same clinical isolate.

Methods

Five-week-old, Choice hybrid pigs were inoculated on 2 consecutive days by intravenous route (Group IV-IV) or by intravenous and intraperitoneal routes (Group IV-IP). Mock-infected animals were used as control (control group). After the challenge, the clinical signs were recorded for 28 days, after which the animals were euthanized. Gross pathological and histopathological examinations, PCR detection, isolation, and genotyping of the re-isolated Mycoplasma sp. and culture of bacteria other than Mycoplasma sp. were carried out. The ELISA test was used to detect anti-M. hyorhinis immunoglobulins in the sera of all animals.

Results

Pericarditis and polyarthritis were observed in both challenge groups; however, the serositis was more severe in Group IV-IV. Statistically significant differences were detected between the challenged groups and the control group regarding the average daily weight gain, pathological scores, and ELISA titers. Additionally, histopathological scores in Group IV-IV differed significantly from the scores in the control group. All re-isolated strains were the same or a close genetic variant of the original challenge strain.

Discussion

Our results indicate that both challenge routes are suitable for modeling the disease. However, due to the evoked more severe pathological lesions and the application being similar to the hypothesized natural route of infection in Group IV-IV, the two-dose intravenous challenge is recommended by the authors to induce serositis and arthritis associated with M. hyorhinis infection.

Preparation of Squalene Oil-Based Emulsion Adjuvants Employing a Self-Emulsifying Drug Delivery System and Assessment of Mycoplasma hyopneumoniae-Specific Antibody Titers in BALB/c Mice

In this study, a self-emulsifying drug delivery system (SEDDS) was employed to prepare novel squalene oil-based emulsion adjuvants. Deionized water, 0.01% and 0.02% (w/v) carbomer solutions of C-971P NF and C-940 grades were used to prepare emulsions containing 3%, 5% and 10% of squalene oil. Altogether 15 candidate emulsions were prepared and used as adjuvants for the delivery of a combination vaccine containing a porcine circovirus type 2 (PCV2) antigen and inactivated Mycoplasma hyopneumoniae (J101 strain) antigen. Most of the emulsions showed droplet sizes in the submicron range and maintained zeta potential values between -40 mV to 0 mV for six months, indicating good physical stability as a vaccine adjuvant. Emulsion-based candidate adjuvants prepared with SEDDS technology stimulated IgG, IgG1 and IgG2a like a currently commercially available adjuvant, Montanide ISA^TM 201, and they were safe and their Mycoplasma hyopneumoniae-specific antibody titers were considered as comparable with that of Montanide ISA^TM 201.

Determination of Mycoplasma hyopneumoniae-Specific IgG, IgG1, and IgG2a Titers in BALB/c Mice Induced by Mineral Oil-Based Oil-in-Water Emulsion Adjuvants Prepared Using a Self-Emulsifying Drug Delivery System

We prepared mineral oil-based emulsion adjuvants by employing simple self-emulsifying drug delivery system (SEDDS). Mineral oil emulsions (3%, 5%, and 7%) were prepared using deionized water and C-971P NF and C-940 grade carbomer solutions with concentrations 0.01% (w/v) and 0.02% (w/v). In total, 15 emulsions were prepared and mixed with a solution containing inactivated Mycoplasma hyopneumoniae (J101 strain) antigen and porcine circovirus type 2 antigen to prepare vaccines. Droplet sizes in the submicron range and zeta potential values between - 40 and 0 mV were maintained by most emulsion adjuvants for a period of 6 months. Emulsion adjuvants were regarded safe, and their M. hyopneumoniae-specific IgG, IgG1, and IgG2a titers were either better or comparable to those of aluminum gel.

Antibody response detected by immunoblot in respiratory tract washings of chickens after infection with Mycoplasma gallisepticum

Two experiments were conducted to test the sensitivity of Western blotting for detection of M. gallisepticum antibodies in respiratory washings and sera of infected chickens by mouse monoclonal antibodies to chicken IgG, IgM and IgA. In the first experiment, birds infected at 10 days of age were examined 2 weeks later. In the respiratory washings, IgA antibodies reacted with eight polypeptides of M. gallisepticum, while IgM and IgG reacted with three. In the serum IgA antibodies were not detected but IgM antibodies reacted with eight polypeptides and IgG with 16. In the second experiment birds were infected at 3 weeks of age and a subgroup was examined every week for 3 weeks post-infection. In the respiratory washings IgA was the principle immunoglobulin detected in the first week and it reacted to six major polypeptides of M. gallisepticum (p72, p64-67, p60, p56, p45, p40). In serum IgM was predominant in the first week and reacted to nine polypeptides. From the second week IgG antibodies were the most important as they reacted to 13 polypeptides in respiratory washings and to 11 polypeptides in the serum, while they reacted to nine polypeptides in respiratory washings and to 13 in the serum in the third week.

Detection and identification of avian mycoplasmas by polymerase chain reaction and restriction fragment length polymorphism assay

The polymerase chain reaction (PCR) with primers complementary to the 16S rRNA genes was used to detect avian mycoplasmas. A primer pair designed for the detection of human and rodent mycoplasmal species was examined for its ability to detect the most important avian mycoplasmas. After testing the respective reference strains, we found that Mycoplasma iowae, Mycoplasma meleagridis and Mycoplasma synoviae could be detected by PCR with this primer pair, and distinction could be made among them by restriction fragment length polymorphism (RFLP) assay with two restriction enzymes (BamHI and RsaI). For the detection of Mycoplasma gallisepticum by PCR, we needed species-specific primers. The results of the PCR- and RFLP, based identification procedures of 17 different field isolates agreed with those obtained by conventional methods.

Immunoblot examination of humoral response of chickens infected with Mycoplasma gallisepticum at various ages

Mycoplasma gallisepticum- and Mycoplasma synoviae-free chickens were infected with 0.2 ml broth culture of M. gallisepticum strain 1226 intra air sac at 3, 14, 18, 28, 42, 49 and 65 days of age. Blood samples were taken 0-5 weeks before infection and 1-6 weeks after infection (depending on age of infection). The antibody response was examined by Western blot. As a control of infection, serum plate agglutination test (SPA), pathological lesions, and presence of Mycoplasma in air sacs were used. Antibodies to p64-67 kDa appeared in all groups of birds on the first week post-infection. Antibodies to p56 were detected from the second week post-challenge if infection was performed at 3 or 14 days of age, while on first week if challenge was done at 18, 28, 42, 49 or 65 days of age. Antibodies to p200, p120, p98, p80, p75, p72, p60, p50, p45, p40, p35, p33, p31, p28, p26, p24 and p22 were also detected.